While employed at Goddard College Chickering began the research that lead to his most notable publication, Education and Identity. Between 1959 and 1969 he did testing on college students between their sophomore and senior years. Compiling this with data from several other dissimilar colleges he gathered through being the director of the Project on Student Development in Small Colleges, he created his theories of what influences and affects college students in their development. He published in 1969 which explained his seven-vector theory of student development. With the help of Linda Reisser, he updated and republished his theories in 1993.[2]